Anchored stress-generating active semiconductor regions for semiconductor-on-insulator finfet

ABSTRACT

After formation of a gate structure and a gate spacer, portions of an insulator layer underlying a semiconductor fin are etched to physically expose semiconductor surfaces of an underlying semiconductor material layer from underneath a source region and a drain region. Each of the extended source region and the extended drain region includes an anchored single crystalline semiconductor material portion that is in epitaxial alignment to the single crystalline semiconductor structure of the underlying semiconductor material layer and laterally applying a stress to the semiconductor fin. Because each anchored single crystalline semiconductor material portion is in epitaxial alignment with the underlying semiconductor material layer, the channel of the fin field effect transistor is effectively stressed along the lengthwise direction of the semiconductor fin.

BACKGROUND

The present disclosure relates to a semiconductor structure, and moreparticularly to a fin field effect transistor on asemiconductor-on-insulator substrate that includes stress-generatingactive semiconductor regions anchored to an underlying semiconductorlayer, and a method of manufacturing the same.

Stress in a channel region of a fin field effect transistor can enhancethe performance of the fin field effect transistor by increasing themobility of minority charge carriers within the channel region. For finfield effect transistors formed on a semiconductor-on-insulator (SOI)substrate, the only physically exposed semiconductor surfaces aresurfaces of source regions and drain regions of the SOI fin field effecttransistor. Any stress applied by the semiconductor stressor elementstends to be applied along the direction of the width of thesemiconductor fin. Thus, attempts to incorporate semiconductor stressorelements into a fin field effect transistor on an SOI substrate havebeen largely unsuccessful so far.

SUMMARY

After formation of a gate structure and a gate spacer, portions of aninsulator layer underlying a semiconductor fin are etched to physicallyexpose semiconductor surfaces of an underlying semiconductor materiallayer from underneath a source region and a drain region. Thecrystallographic orientations of the physically exposed semiconductorsurfaces and sidewall surfaces of the semiconductor fin are selectedsuch that epitaxial growth can proceed faster from the physicallyexposed semiconductor surface of the underlying semiconductor materiallayer than from sidewalls of the semiconductor fin. Each of the extendedsource region and the extended drain region includes an anchored singlecrystalline semiconductor material portion that is in epitaxialalignment to the single crystalline semiconductor structure of theunderlying semiconductor material layer and laterally applying a stressto the semiconductor fin. Because each anchored single crystallinesemiconductor material portion is in epitaxial alignment with theunderlying semiconductor material layer, the channel of the fin fieldeffect transistor is effectively stressed along the lengthwise directionof the semiconductor fin.

According to an aspect of the present disclosure, a semiconductorstructure includes a single crystalline semiconductor material layerlocated in a substrate. An insulator layer contacts a top surface of thesingle crystalline semiconductor material layer. A semiconductor fincontacts a portion of a top surface of the insulator layer. A gate stackcontacts another portion of the top surface of the insulator layer, andstraddles the semiconductor fin. A gate spacer laterally surrounds thegate stack and straddles the semiconductor fin. An extended sourceregion contacts, and is epitaxially aligned to, a first portion of thetop surface of the single crystalline semiconductor material layer, andcontacts a first end portion of the semiconductor fin laterallyprotruding from a first outer sidewall of the gate spacer. An extendeddrain region contacts, and is epitaxially aligned to, a second portionof the top surface of the single crystalline semiconductor materiallayer, and contacts a second end portion of the semiconductor finlaterally protruding from a second outer sidewall of the gate spacer.

According to another aspect of the present disclosure, a method offorming a semiconductor structure is provided. A semiconductor fin isformed on a stack, from bottom to top, of a single crystallinesemiconductor material layer and an insulator layer. A gate stack isformed over the semiconductor fin. A gate spacer is formed around thegate stack. A first portion and a second portion of a top surface of thesingle crystalline semiconductor material layer are physically exposed.An extended source region is formed on the first portion and an extendeddrain region is formed on the second portion by selective deposition ofan epitaxial semiconductor material on the first portion, the secondportion, and physically exposed surfaces of the semiconductor fin.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a top-down view of a first exemplary semiconductor structureafter formation of a plurality of semiconductor fins according to afirst embodiment of the present disclosure.

FIG. 1B is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 1A.

FIG. 1C is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 1A.

FIG. 1D is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane D-C′ in FIG. 1A.

FIG. 2A is a top-down view of the first exemplary semiconductorstructure after formation of a gate stack according to the firstembodiment of the present disclosure.

FIG. 2B is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 2A.

FIG. 2C is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 2A.

FIG. 2D is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 2A.

FIG. 3A is a top-down view of the first exemplary semiconductorstructure after formation of a source region, a drain region, and a gatespacer according to the first embodiment of the present disclosure.

FIG. 3B is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 3A.

FIG. 3C is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 3A.

FIG. 3D is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 3A.

FIG. 4A is a top-down view of the first exemplary semiconductorstructure after application and patterning of a photoresist layer andformation of openings through an insulator layer according to the firstembodiment of the present disclosure.

FIG. 4B is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 4A.

FIG. 4C is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 4A.

FIG. 4D is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 4A.

FIG. 5A is a top-down view of the first exemplary semiconductorstructure after formation of an extended source region and an extendeddrain region according to the first embodiment of the presentdisclosure.

FIG. 5B is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 5A.

FIG. 5C is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 5A.

FIG. 5D is a vertical cross-sectional view of the first exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 5A.

FIG. 6A is a top-down view of a variation of the first exemplarysemiconductor structure after anisotropically etching through theinsulator layer according to the first embodiment of the presentdisclosure.

FIG. 6B is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane B-B′ in FIG.6A.

FIG. 6C is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane C-C′ in FIG.6A.

FIG. 6D is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane D-D′ in FIG.6A.

FIG. 7A is a top-down view of a variation of the variation of the firstexemplary semiconductor structure after formation of an activesemiconductor material layer and application and patterning of aphotoresist layer according to the first embodiment of the presentdisclosure.

FIG. 7B is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane B-B′ in FIG.7A.

FIG. 7C is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane C-C′ in FIG.7A.

FIG. 7D is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane D-D′ in FIG.7A.

FIG. 8A is a top-down view of a variation of the variation of the firstexemplary semiconductor structure after patterning of the activesemiconductor material layer into an extended source region and anextended drain region and removal of the photoresist layer according tothe first embodiment of the present disclosure.

FIG. 8B is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane B-B′ in FIG.8A.

FIG. 8C is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane C-C′ in FIG.8A.

FIG. 8D is a vertical cross-sectional view of the variation of the firstexemplary semiconductor structure along the vertical plane D-D′ in FIG.8A.

FIG. 9A is a top-down view of a second exemplary semiconductor structureafter a lateral etch of the insulator layer according to the secondembodiment of the present disclosure.

FIG. 9B is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 9A.

FIG. 9C is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 9A.

FIG. 9D is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 9A.

FIG. 10A is a top-down view of the second exemplary semiconductorstructure after formation of an extended source region and an extendeddrain region according to the second embodiment of the presentdisclosure.

FIG. 10B is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane B-B′ in FIG. 10A.

FIG. 10C is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane C-C′ in FIG. 10A.

FIG. 10D is a vertical cross-sectional view of the second exemplarysemiconductor structure along the vertical plane D-D′ in FIG. 10A.

DETAILED DESCRIPTION

As stated above, the present disclosure relates to a fin field effecttransistor on a semiconductor-on-insulator substrate that includesstress-generating active semiconductor regions anchored to an underlyingsemiconductor layer, and a method of manufacturing the same. Aspects ofthe present disclosure are now described in detail with accompanyingfigures. It is noted that like reference numerals refer to like elementsacross different embodiments. The drawings are not necessarily drawn toscale.

Referring to FIGS. 1A-1D, an exemplary semiconductor structure accordingto an embodiment of the present disclosure includes a single crystallinesemiconductor material layer 10, an insulator layer 20, and a pluralityof semiconductor fins 30 on the insulator layer. The single crystallinesemiconductor material layer 10 includes a first semiconductor material.The single crystalline semiconductor material layer 10 can be a singlecrystalline material portion of the first semiconductor material. Thefirst semiconductor material can be, for example, silicon, germanium,silicon-germanium alloy, silicon carbon alloy, silicon-germanium-carbonalloy, gallium arsenide, indium arsenide, indium phosphide, other III-Vcompound semiconductor materials, II-VI compound semiconductormaterials, organic semiconductor materials, and other compoundsemiconductor materials. In an exemplary case, the semiconductormaterial comprises single crystalline silicon. The insulator layer 20includes a dielectric material such as silicon oxide, silicon nitride,and/or silicon oxynitride. In one embodiment, a top surface of thesingle crystalline semiconductor material layer 10 can have a (001)surface orientation.

The plurality of semiconductor fins 30 includes a second semiconductormaterial. The second semiconductor material may be selected from, but isnot limited to, silicon, germanium, silicon-germanium alloy, siliconcarbon alloy, silicon-germanium-carbon alloy, gallium arsenide, indiumarsenide, indium phosphide, other III-V compound semiconductormaterials, II-VI compound semiconductor materials, organic semiconductormaterials, and other compound semiconductor materials. In an exemplarycase, the semiconductor material can include single crystalline siliconor a single crystalline alloy of silicon. In one embodiment, thesemiconductor material in each of the plurality of semiconductor fins 30can be single crystalline. The semiconductor material of the pluralityof semiconductor fins 30 can be the same as, or different from, thesemiconductor material of the single crystalline semiconductor materiallayer 10.

The plurality of semiconductor fins 30 can be formed, for example, bypatterning a single crystalline semiconductor layer. In one embodiment,the single crystalline semiconductor layer can be a top semiconductorlayer within a semiconductor-on-insulator (SOI) substrate including avertical stack of the single crystalline semiconductor material layer10, the insulator layer 20, and the top semiconductor layer. Forexample, a patterned photoresist layer can be formed over the topsemiconductor layer of the SOI substrate and the top semiconductor layercan be patterned into the plurality of semiconductor fins 30 bytransferring the pattern in the patterned photoresist layer with ananisotropic etch. Dielectric fin caps (not shown) having the samehorizontal cross-sectional area as an underlying semiconductor fin 30may be optionally formed on the top surface of each semiconductor fin30.

In one embodiment, the plurality of semiconductor fins 30 may be dopedwith p-type dopants or n-type dopants. If the plurality of semiconductorfins 30 is doped, the type of doping of the plurality of semiconductorfins 30 is herein referred to as a first conductivity type. Theelectrical dopants may be at least one of p-type dopants such as B, Ga,and In. Alternately, the electrical dopants may be at least one ofn-type dopants such as P, As, and Sb. The concentration of theelectrical dopants (p-type dopants or n-type dopants) in the pluralityof semiconductor fins 30 may be from 1.0×10¹⁵ atoms/cm³ to 1.0×10¹⁹atoms/cm³, although lesser and greater concentrations can also beemployed. Non-electrical stress-generating dopants such as Ge and/or Cmay also be present in the plurality of semiconductor fins 30 in someembodiments.

In one embodiment, the semiconductor material layer from which theplurality of semiconductor fins 30 is patterned can have a (001) surfaceorientation. Further, the orientations of the plurality of semiconductorfins 30 can be selected such that each of the plurality of semiconductorfins 30 includes a (001) top surface, (110) sidewall surfaces, and (110) end walls. As used herein, sidewall surfaces refer to verticalsurfaces laterally extending along the lengthwise direction of asemiconductor fin, and end surfaces refer to vertically surfaces thatare perpendicular to the lengthwise direction of the semiconductor fin.As used herein, a lengthwise direction of an object refers to thedirection along which the moment of inertia of the object has theminimum value.

The height of the plurality of semiconductor fins can be from 20 nm to300 nm, although greater and lesser thicknesses can also be employed.The width of each semiconductor fin 30 along the horizontal directionincluded in the vertical plane B-B′ can be from 3 nm to 100 nm, althoughlesser and greater widths can also be employed. The length of eachsemiconductor fin 30 along the direction perpendicular to the verticalplane B-B′ can be from 60 nm to 1,000 nm, although lesser and greaterlengths can also be employed.

Referring to FIGS. 2A-2D, a gate dielectric 50, a gate electrode 52, anda gate cap dielectric 58 are formed over a middle portion of eachsemiconductor fin 30 by deposition and patterning of a gate dielectriclayer, a gate conductor layer, and a gate cap dielectric layer. The gatedielectric layer can be formed conformally on the surfaces of theplurality of semiconductor fins 30.

In one embodiment, the gate dielectric layer can include a dielectricmaterial formed by thermal conversion of a portion of the semiconductorfin, such as silicon oxide or silicon nitride. Thermal oxidation,thermal nitridation, plasma oxidation, plasma nitridation, or acombination thereof may be employed to form the gate dielectric layer.In this case, the gate dielectric layer can be formed only on physicallyexposed surfaces of the plurality of semiconductor fin 30.

Alternately or additionally, the gate dielectric layer may include ahigh-k dielectric material having a dielectric constant greater than3.9, i.e., the dielectric constant of silicon oxide. The high-kdielectric material may comprise a dielectric metal oxide containing ametal and oxygen. In one embodiment, the dielectric constant of thehigh-k material is greater than or about 4.0. In one embodiment, thedielectric constant of the high-k dielectric material is greater thanthe dielectric constant of silicon nitride, which is about 7.5. In oneembodiment, the dielectric constant of the high-k dielectric material isgreater than 8.0. The high-k dielectric materials are also known in theart as high-k gate dielectric materials, which include dielectric metaloxides, alloys thereof, and silicate alloys thereof. Exemplary high-kdielectric materials include HfO₂, ZrO₂, La₂O₃, Al₂O₃, TlO₂, SrTiO₃,LaAlO₃, Y₂O₃, HfO_(x)N_(y), ZrO_(x)N_(y), La₂O_(x)N_(y), Al₂O_(x)N_(y),TiO_(x)N_(y), SrTiO_(x)N_(y), LaAlO_(x)N_(y), Y₂O_(x)N_(y), a silicatethereof, and an alloy thereof. Each value of x can be independently fromabout 0.5 to about 3 and each value of y can be independently from 0 toabout 2. Optionally, an interfacial layer (not shown), for example,silicon oxide, can be formed by chemical oxidation or thermal oxidationbefore the high-k dielectric material is deposited.

The gate conductor layer can be deposited on the gate dielectric layer,for example, by chemical vapor deposition (CVD). The gate conductorlayer may comprise a doped semiconductor material or a metallicmaterial. Non-limiting examples of the semiconductor materials includeamorphous silicon, polysilicon, an amorphous silicon germanium alloy, ora polycrystalline silicon germanium alloy. Non-limiting examples ofmetallic materials include W, Ta, TiN, ZrN, HfN, VN, NbN, TaN, WN,TiAlN, TaC, TaMgC, TaCN, other conductive refractory metal nitrides, andan alloy thereof. The gate conductor layer may be formed by chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), vacuum evaporation, etc. In one embodiment, thethickness of the gate conductor layer may be from 20 nm to 300 nm.

The gate cap dielectric layer can be formed by deposition of adielectric material. In one embodiment, the dielectric material of thegate cap dielectric layer can be silicon nitride. The thickness of thegate cap dielectric layer can be in a range from 20 nm to 300 nm,although lesser and greater thicknesses can also be employed.

The stack of the gate dielectric layer, the gate conductor layer, andthe gate cap dielectric layer can be lithographically patterned byapplication and patterning of a photoresist material, and by transfer ofthe pattern in the photoresist material into the stack. Employing thepatterned photoresist as an etch mask, the anisotropic etch can removethe physically exposed portions of the gate cap dielectric layer and thegate conductor layer selective to the gate dielectric layer. The exposedportions of the gate dielectric layer can subsequently be removedselective to the semiconductor material of the plurality ofsemiconductor fins 30, for example, by an isotropic etch such as a wetetch. A remaining portion of the gate cap dielectric layer constitutes agate cap dielectric 58, a remaining portion of the gate conductor layerconstitutes a gate electrode 52, and a remaining portion of the gatedielectric layer constitutes a gate dielectric 50. The gate dielectric50, the gate electrode 52, and the gate cap dielectric 58 constitute agate stack (50, 52, 58).

Referring to FIGS. 3A-3D, electrical dopants can be implanted to form asource region 3S and a drain region 3D. The gate stack (50, 52, 58) canbe employed as an implantation mask during the implantation of theelectrical dopants. The unimplanted regions of the semiconductor fin 30constitute body regions 3B. Each body region 3B can be intrinsic, or canbe doped with electrical dopants of a first conductivity type, which canbe p-type or n-type. If the body region 3B has a doping of the firstconductivity type, the source region 3S and the drain region 3D has adoping of a second conductivity type, which is the opposite conductivitytype of the first conductivity type. For example, if the firstconductivity type is p-type, the second conductivity type is n-type, orvice versa.

As used herein, a source region 3S includes any doped region located onone side of the body region 3B and having a different type of dopingthan the body region 3B, which is intrinsic (i.e., does not have anydoping) or has a doping of the first conductivity type. As such, eachsource region 3S can include a source extension region as known in theart. As used herein, a drain region 3D includes any doped region locatedon the opposite side of the body region 3B and having a different typeof doping than the body region 3B. As such, each drain region 3D caninclude a drain extension region as known in the art.

A gate spacer 54 can be formed around each gate stack (50, 52, 58). Thegate spacers 54 can be formed, for example, by depositing a conformaldielectric material layer and by anisotropically etching the conformaldielectric material layer by an anisotropic etch. The anisotropic etchrecesses the portions of the conformal dielectric material layer locatedon sidewalls of the semiconductor fins 30 and are laterally spaced fromthe gate electrodes (50, 52, 58) by a distance greater than thethickness of the conformal dielectric layer. The remaining verticalportions of the conformal dielectric material layer constitute the gatespacers 54. Sidewalls of the semiconductor fins 30 are physicallyexposed after formation of the gate spacer 54.

Referring to FIGS. 4A-4D, a photoresist layer 67 is applied over thegate stacks (50, 52, 58), the gate spacers 54, and the insulator layer20, and is lithographically patterned to cover regions in whichformation of extended active regions is to be suppressed. As usedherein, extended active regions collectively refer to extended sourceregions that are electrically shorted to source regions and including adoped semiconductor material and extended drain regions that areelectrically shorted to drain regions and including a dopedsemiconductor material. In one embodiment, the photoresist layer 67 cancover end portions of the gate stacks (50, 52, 58) that do not overliethe semiconductor fins 30, and physically expose regions that overliethe semiconductor fins 30.

An anisotropic etch is performed to remove physically exposed portionsof the insulator layer 20. The anisotropic etch can employ thecombination of the gate stacks (50, 52, 58), the gate spacers 54, andthe photoresist layer 67 as an etch mask. A first opening 21A throughthe insulator layer 20 can be formed on a first side of the gate spacers54 within an area laterally bounded by sidewalls of the source regions3S, a sidewall of the gate spacer 54, and sidewalls of the photoresistlayer 67. A first portion of the top surface of the single crystallinesemiconductor material layer 10 is physically exposed at a bottomportion of the first opening 21A. A second opening 21B through theinsulator layer 20 can be formed on a second side of the gate spacers 54within an area laterally bounded by sidewalls of the drain regions 3D, asidewall of the gate spacer 54, and sidewalls of the photoresist layer67. A second portion of the top surface of the single crystallinesemiconductor material layer 10 is physically exposed at a bottomportion of the second opening 21B.

Each of the first opening 21A and the second opening 21B extends to thesingle crystalline semiconductor material layer 10 through the insulatorlayer 20. An edge at which the first opening 21A adjoins the top surfaceof the insulator layer 20 can be vertically coincident with the firstouter sidewall of the gate spacer 54, and an edge at which the secondopening 21B adjoins the top surface of the insulator layer 20 can bevertically coincident with the second outer sidewall of the gate spacer54. The photoresist layer 67 is subsequently removed, for example, byashing.

Referring to FIGS. 5A-5D, a semiconductor material can be deposited oneach physically exposed portion of the single crystalline semiconductormaterial layer 10 and each physically exposed end surface of thesemiconductor fins (3B, 3S, 3D). At least one extended source region 60Sand at least one extended drain region 60D can be formed, for example,by selective epitaxy of a semiconductor material. The extended sourceregion 60S and an extended drain region 60D can be formed on portions ofthe top surface of the single crystalline semiconductor material layer10 and the physically exposed surfaces of the semiconductor fins 30 byselective deposition of an epitaxial semiconductor material. In anillustrative example, an extended source region 60S can be formed on afirst portion of the single crystalline semiconductor material layer 10underneath the first opening 21A (See FIG. 4B) and on the surfaces ofthe source regions 3S, and an extended drain region 60D can be formed ona second portion of the single crystalline semiconductor material layer10 underneath the second opening 21B (See FIG. 4B) and on the surfacesof the drain regions 3D. In one embodiment, the extended source region60S can be formed on a sidewall of the insulator layer 20 that isvertically coincident with a sidewall of a semiconductor fin (3B, 3S,3D), and the extended drain region 60D can be formed on another sidewallof the insulator layer 20 that is vertically coincident with a sidewallof the semiconductor fin (3B, 3S, 3D).

In one embodiment, each extended source region 60S and each extendeddrain region 60D can include single crystalline semiconductor materialportions that are epitaxially aligned to the second semiconductormaterial of the semiconductor fins (3B, 3S, 3D) or the firstsemiconductor material of the single crystalline semiconductor materiallayer 10. As used herein, “epitaxial” alignment refers to alignment ofatoms in a same singe crystalline structure. For example, each of thesemiconductor fins (3B, 3S, 3D) and the single crystalline semiconductormaterial layer 10 can be single crystalline, and each of the sourceregions 60S and the drain regions 60D can include a portion that isepitaxially aligned to the single crystalline semiconductor materiallayer 10 and at least another portion that is epitaxially aligned to asemiconductor fin (3B, 3S, 3D).

The semiconductor material of each extended source region 60S and eachextended drain region 60D can be the same as, or different from, thesecond semiconductor material, i.e., the semiconductor material of theplurality of semiconductor fins (3B, 3S, 3D). Further, the semiconductormaterial of each extended source region 60S and each extended drainregion 60D can be the same as, or different from, the firstsemiconductor material, i.e., the semiconductor material of the singlecrystalline semiconductor material layer 10.

In selective epitaxy, the exemplary semiconductor structure can beplaced in a process chamber. A reactant gas including a precursor gasfor a semiconductor material is flowed into the process chambersimultaneously with, or alternately with, an etchant gas that etches asemiconductor material. The net deposition rate on the depositedsemiconductor material is the difference between the deposition rate ofa semiconductor material due to the reactant gas less the etch rate ofthe semiconductor material due to the etchant gas. The selective epitaxyprocess does not deposit any semiconductor material on dielectricsurfaces such as the surfaces of the inner gate spacer 54 or the surfaceof the insulator layer 20 because any semiconductor material thatnucleates on the dielectric surfaces is etched by the etchant gas beforea contiguous layer of a deposited semiconductor material can be formedon the dielectric surfaces.

The reactant gas can be, for example, SiH₄, SiH₂Cl₂, SiHCl₃, SiCl₄,Si₂H₆, GeH₄, Ge₂H₆, CH₄, C₂H₂, or combinations thereof. The etchant gascan be, for example, HCl. A carrier gas such as H₂, N₂, or Ar can beemployed in conjunction with the reactant gas and/or the etchant gas.

In one embodiment, each extended source region 60S and each extendeddrain region 60D can be formed with in-situ doping so that each extendedsource region 60S and each extended drain region 60D are doped withelectrical dopants during the selective epitaxy. The extended sourceregion 60S and the extended drain region 60D can be doped withelectrical dopants of the second conductivity type, which is theopposite of the first conductivity type. Thus, the extended sourceregion 60S and the extended drain region 60D are doped with dopants ofthe same conductivity type as dopants implanted into the source regions3S and the drain regions 3D. For example, if the first conductivity type(which is the conductivity type of the plurality of semiconductor fins30) is p-type, the second conductivity type is n-type, and vice versa.

Alternately, each extended source region 60S and each extended drainregion 60D can be formed without doping so that each extended sourceregion 60S and each extended drain region 60D are formed as intrinsicsemiconductor material portions. In this case, electrical dopants can beintroduced into the extended source region 60S and the extended drainregion 60D in a subsequent processing step.

In one embodiment, grain boundaries may be present within each extendedsource region 60S and each extended drain region 60D because eachextended source region 60S or each extended drain region 60D can includea plurality of single crystalline grains that grow from different singlecrystalline surfaces. For example, each extended source region 60S oreach extended drain region 60D can include a single crystalline grainthat grows from a surface of the single crystalline semiconductormaterial layer 10, and a plurality of grains that grow from differentend surfaces of semiconductor fins (3B, 3S, 3D). In this case, each ofthe extended source region 60S and the extended drain region 60D caninclude a portion that is epitaxially aligned to the single crystallinesemiconductor material layer 10 and at least another portion that isepitaxially aligned to a semiconductor fin (3B, 3S, 3D). In oneembodiment, at least one grain boundary can contact the verticalsidewalls of the insulator layer 20.

In one embodiment, the top surface of the single crystallinesemiconductor material layer 10 can have a (001) surface, and each ofthe semiconductor fins (3B, 3S, 3D) can includes a (001) top surface,(110) sidewall surfaces, and (1 10) end walls. In this case, epitaxialgrowth along the <001> direction can proceed at a rate that is at least1.5 times the epitaxial growth rate along the <110> directions, and theangle of the grain boundaries relative the vertical direction can beless than 45 degrees. In this case, within each of the extended sourceregion 60S and the extended drain region 60D, a grain boundary between aportion that is epitaxially aligned to the single crystallinesemiconductor material layer 10 and another portion that is epitaxiallyaligned to a semiconductor fin (3B, 3S, 3D) can extends from a surfaceof the insulator layer 20 to a top surface of the extended source region60S or to a top surface of the extended drain region 60D.

The first exemplary semiconductor structure includes the singlecrystalline semiconductor material layer 10 located in a substrate, theinsulator layer 20 contacting the top surface of the single crystallinesemiconductor material layer 30, and at least a semiconductor fin (3B,3S, 3D) contacting a portion of the top surface of the insulator layer20. The gate stack (50, 52, 58) includes the gate dielectric 50 and thegate electrode 52, contacts another portion of the top surface of theinsulator layer 20, and straddles each semiconductor fin (3B, 3S, 3D).The gate spacer 54 laterally surrounds the gate stack (50, 52, 58) andstraddles the semiconductor fin(s) (3B, 3S, 3D). The extended sourceregion 60S contacts, and is epitaxially aligned to, a first portion ofthe top surface of the single crystalline semiconductor material layer10, and contacts a first end portion (that includes a source region 3S)of each semiconductor fin (3B, 3S, 3D) laterally protruding from a firstouter sidewall 54A of the gate spacer 54. The extended drain region 60Dcontacts, and is epitaxially aligned to, a second portion of the topsurface of the single crystalline semiconductor material layer 10, andcontacts a second end portion (that includes a drain region 3D) of eachsemiconductor fin (3B, 3S, 3D) laterally protruding from a second outersidewall 54B of the gate spacer 54.

In one embodiment, the extended source region 60S can contact the firstouter sidewall 54A of the gate spacer 54, and the extended drain region60D can contact the second outer sidewall 54B of the gate spacer 54.Each semiconductor fin (3B, 3S, 3D) can include a body region 3B, asource region 3S located in the first end portion and contacting thebody region 3B, and a drain region 3D located in the second end portionand contacting the body region 3B and laterally spaced from the sourceregion 3S. The source regions 3S, the drain regions 3D, the extendedsource region 60S, and the extended drain region 60D can have the sametype of doping. Sidewalls and end walls of the insulator layer 20 can bevertically coincident with end walls and sidewalls of the first endportion and the second end portion of the semiconductor fins (3B, 3S,3D).

The extended source region 60S and the extended drain region 60D caninclude a semiconductor material that is lattice mismatched to thesecond semiconductor material, i.e., a semiconductor material that has adifferent lattice constant than the second semiconductor material. Inthis case, the extended source region 60S and the extended drain region60D can apply a compressive stress or a compressive strain in the bodyregions 3B of the semiconductor fins (3B, 3S, 3D) along the lengthwisedirection of the semiconductor fins (3B, 3S, 3D). The compressive ortensile stress, and the resulting compressive or tensile strain, alongthe direction of current flow between each pair of a source region 3Sand a drain region 3D in the same semiconductor fin (3B, 3S, 3D).

Further, the extended source region 60S and the extended drain region60D are not free to change volumes because each of the extended sourceregion 60S and the extended drain region 60D includes a singlecrystalline material portion that is epitaxially aligned to the firstsemiconductor material of the single crystalline semiconductor materiallayer 10. The single crystalline material portion that is epitaxiallyaligned to the first semiconductor material of the single crystallinesemiconductor material layer 10 functions as a structural anchor thatprevents relaxation of the lattice constant in the portions of theextended source region 60S and the extended drain region 60D that areepitaxially aligned to the source regions 3S or the drain regions 3D.Therefore, transmission of a compressive stress or a tensile stress fromthe extended source region 60S or the extended drain region 60D to thebody regions 3B is more effective due to the epitaxial alignment of theportions of the extended source region 60S or the extended drain region60D that are epitaxially aligned to the single crystalline semiconductormaterial layer 10.

Referring to FIGS. 6A-6D, a variation of the first exemplarysemiconductor structure can be derived from the first exemplarysemiconductor structure of FIGS. 3A-3D by performing the processingsteps of FIGS. 4A-4D without employing the photoresist layer 67 (SeeFIGS. 4A-4D). Thus, the anisotropic etch process that etches physicallyexposed portions of the insulator layer 20 is performed employing thecombination of the gate stacks (50, 52, 48), the semiconductor fins (3B,3S, 3D), and the gate spacers 54 as an etch mask.

All areas of the top surface of the single crystalline semiconductormaterial layer 10 that do not underlie the gate stack (50, 52, 58), thegate spacer 54, or the semiconductor fins (3B, 3S, 3D) can be physicallyexposed after the anisotropic etch. A first portion of the top surfaceof the single crystalline semiconductor material layer 10 is physicallyexposed around the sidewalls of the source regions 3S, and a secondportion of the top surface of the single crystalline semiconductormaterial layer 10 is physically exposed around the sidewalls of thedrain regions 3D.

Referring to FIGS. 7A-7D, the selective deposition step of FIGS. 5A-5Dis subsequently performed to form an active semiconductor material layer60L. The active semiconductor material layer 60L can include the samesemiconductor material as the extended source region 60S and theextended drain region 60D shown in FIGS. 5A-5D. The active semiconductormaterial layer 60L can include a portion epitaxially aligned to thephysically exposed top surface of the single crystalline semiconductormaterial layer 10 and portions that are epitaxially aligned to thesemiconductor fins (3B, 3S,3D). The active semiconductor material layer60L is doped with dopants of the second conductivity type by in-situdoping or ex-situ doping.

A photoresist layer 77 is applied over the active semiconductor materiallayer 60L, and is lithographically patterned to cover areas in which anextended source region 60S and an extended drain region 60D are to beformed.

Referring to FIGS. 8A-8D, the deposited semiconductor material of theactive semiconductor material layer 60L is patterned employing thepatterned photoresist layer 77 as an etch mask. Physically exposedportions of the active semiconductor material layer 60L can be removedby an anisotropic etch. Portions of the top surface of the singlecrystalline semiconductor material layer 10 can be physically exposedafter patterning the deposited semiconductor material. A first remainingportion of the active semiconductor material layer 60L contacting thesidewalls of the source regions 3S is an extended source region 60S, anda remaining portion of the active semiconductor material layer 60Lcontacting the sidewalls of the drain regions 3D is an extended drainregion 60D. The photoresist layer 77 can be subsequently removed, forexample, by ashing.

In one embodiment, grain boundaries may be present within each extendedsource region 60S and each extended drain region 60D because eachextended source region 60S or each extended drain region 60D can includea plurality of single crystalline grains that grow from different singlecrystalline surfaces. For example, each extended source region 60S oreach extended drain region 60D can include a single crystalline grainthat grows from a surface of the single crystalline semiconductormaterial layer 10, and a plurality of grains that grow from differentend surfaces of semiconductor fins (3B, 3S, 3D). In this case, each ofthe extended source region 60S and the extended drain region 60D caninclude a portion that is epitaxially aligned to the single crystallinesemiconductor material layer 10 and at least another portion that isepitaxially aligned to a semiconductor fin (3B, 3S, 3D). In oneembodiment, at least one grain boundary can contact the verticalsidewalls of the insulator layer 20.

In one embodiment, the top surface of the single crystallinesemiconductor material layer 10 can have a (001) surface, and each ofthe semiconductor fins (3B, 3S, 3D) can includes a (001) top surface,(110) sidewall surfaces, and (1 10) end walls. In this case, epitaxialgrowth along the <001> direction can proceed at a rate that is at least1.5 times the epitaxial growth rate along the <110> directions, and theangle of the grain boundaries relative the vertical direction can beless than 45 degrees. In this case, within each of the extended sourceregion 60S and the extended drain region 60D, a grain boundary between aportion that is epitaxially aligned to the single crystallinesemiconductor material layer 10 and another portion that is epitaxiallyaligned to a semiconductor fin (3B, 3S, 3D) can extends from a surfaceof the insulator layer 20 to a top surface of the extended source region60S or to a top surface of the extended drain region 60D.

Referring to FIGS. 9A-9D, a second exemplary semiconductor structureaccording to the second embodiment of the present disclosure can bederived from the first exemplary semiconductor structure of FIGS. 4A-4Dby laterally etching the insulator layer 20 by an isotropic etch. Theisotropic etch can be a wet etch or a dry etch. The duration of theisotropic etch is controlled so that the portions of the insulator layer20 that protrude from the outer sidewalls (54A, 54B) of the gate spacer54 are removed, while a portion of the insulator layer 20 remainsunderneath the gate stack (50, 52, 58). Each source region 30S includesa physically exposed bottom surface. Each drain region 30D includes aphysically exposed bottom surface. The photoresist layer 67 issubsequently removed, for example, by ashing.

Referring to FIGS. 10A-10D, the processing step of FIGS. 5A-5D isperformed to form an extended source region 60S and an extended drainregion 60D. In one embodiment, grain boundaries may be present withineach extended source region 60S and each extended drain region 60Dbecause each extended source region 60S or each extended drain region60D can include a plurality of single crystalline grains that grow fromdifferent single crystalline surfaces. For example, each extended sourceregion 60S or each extended drain region 60D can include a singlecrystalline grain that grows from a surface of the single crystallinesemiconductor material layer 10, and a plurality of grains that growfrom different end surfaces of semiconductor fins (3B, 3S, 3D). In thiscase, each of the extended source region 60S and the extended drainregion 60D can include a portion that is epitaxially aligned to thesingle crystalline semiconductor material layer 10 and at least anotherportion that is epitaxially aligned to a semiconductor fin (3B, 3S, 3D).In one embodiment, at least one grain boundary can contact the verticalsidewalls of the insulator layer 20.

In one embodiment, the top surface of the single crystallinesemiconductor material layer 10 can have a (001) surface, and each ofthe semiconductor fins (3B, 3S, 3D) can includes a (001) top surface,(110) sidewall surfaces, and (1 10) end walls. In this case, epitaxialgrowth along the <001> direction can proceed at a rate that is at least1.5 times the epitaxial growth rate along the <110> directions, and theangle of the grain boundaries relative the vertical direction can beless than 45 degrees. Within each of the extended source region 60S andthe extended drain region 60D, a grain boundary between the portion thatis epitaxially aligned to the single crystalline semiconductor materiallayer 10 and another portion that is epitaxially aligned to asemiconductor fin (3B, 3S, 3D) can underlie a portion of thesemiconductor fin (3B, 3S, 3D). In this case, within each of theextended source region 60S and the extended drain region 60D, a grainboundary between a portion that is epitaxially aligned to the singlecrystalline semiconductor material layer 10 and another portion that isepitaxially aligned to a semiconductor fin (3B, 3S, 3D) can extends froma surface of the insulator layer 20 to a top surface of the extendedsource region 60S or to a top surface of the extended drain region 60D.The surface from which the grain boundary extends can be a surface ofthe insulator layer 30 that underlies the gate stack (50, 52, 58).

In one embodiment, a grain boundary in the extended source region 60Scan underlie a first end portion of each semiconductor fin (3B, 3S, 3D)that includes a source region 3S, and a grain boundary in the extendeddrain region 60D can underlie a second end portion of each semiconductorfin (3B, 3S, 3D) that includes a drain region 3D.

The extended source region 60S and the extended drain region 60D caninclude a semiconductor material that is lattice mismatched to thesecond semiconductor material, i.e., a semiconductor material that has adifferent lattice constant than the second semiconductor material. Inthis case, the extended source region 60S and the extended drain region60D can apply a compressive stress or a compressive strain in the bodyregions 3B of the semiconductor fins (3B, 3S, 3D) along the lengthwisedirection of the semiconductor fins (3B, 3S, 3D). The compressive ortensile stress, and the resulting compressive or tensile strain, alongthe direction of current flow between each pair of a source region 3Sand a drain region 3D in the same semiconductor fin (3B, 3S, 3D).

Further, the extended source region 60S and the extended drain region60D are not free to change volumes because each of the extended sourceregion 60S and the extended drain region 60D includes a singlecrystalline material portion that is epitaxially aligned to the firstsemiconductor material of the single crystalline semiconductor materiallayer 10. The single crystalline material portion that is epitaxiallyaligned to the first semiconductor material of the single crystallinesemiconductor material layer 10 functions as a structural anchor thatprevents relaxation of the lattice constant in the portions of theextended source region 60S and the extended drain region 60D that areepitaxially aligned to the source regions 3S or the drain regions 3D.Therefore, transmission of a compressive stress or a tensile stress fromthe extended source region 60S or the extended drain region 60D to thebody regions 3B is more effective due to the epitaxial alignment of theportions of the extended source region 60S or the extended drain region60D that are epitaxially aligned to the single crystalline semiconductormaterial layer 10.

While the disclosure has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Each of the embodiments described herein canbe implemented individually or in combination with any other embodimentunless expressly stated otherwise or clearly incompatible. Accordingly,the disclosure is intended to encompass all such alternatives,modifications and variations which fall within the scope and spirit ofthe disclosure and the following claims.

What is claimed is:
 1. A semiconductor structure comprising: a singlecrystalline semiconductor material layer located in a substrate; aninsulator layer contacting a top surface of said single crystallinesemiconductor material layer; a semiconductor fin contacting a portionof a top surface of said insulator layer; a gate stack contactinganother portion of said top surface of said insulator layer, andstraddling said semiconductor fin; a gate spacer laterally surroundingsaid gate stack and straddling said semiconductor fin; an extendedsource region contacting, and epitaxially aligned to, a first portion ofsaid top surface of said single crystalline semiconductor materiallayer, and contacting a first end portion of said semiconductor finlaterally protruding from a first outer sidewall of said gate spacer;and an extended drain region contacting, and epitaxially aligned to, asecond portion of said top surface of said single crystallinesemiconductor material layer, and contacting a second end portion ofsaid semiconductor fin laterally protruding from a second outer sidewallof said gate spacer.
 2. The semiconductor structure of claim 1, whereinsaid extended source region contacts said first outer sidewall of saidgate spacer, and said extended drain region contacts said second outersidewall of said gate spacer.
 3. The semiconductor structure of claim 1,wherein said semiconductor fin comprises a body region, a source regionlocated in said first end portion and contacting said body region, and adrain region located in said second end portion and contacting said bodyregion and laterally spaced from said source region.
 4. Thesemiconductor structure of claim 3, wherein said source region, saiddrain region, said extended source region, and said extended drainregion have a same type of doping.
 5. The semiconductor structure ofclaim 1, wherein said semiconductor fin is single crystalline, and eachof said extended source region and said extended drain region includes aportion that is epitaxially aligned to said semiconductor material layerand another portion that is epitaxially aligned to said semiconductorfin.
 6. The semiconductor structure of claim 1, each grain boundarybetween a portion that is epitaxially aligned to said semiconductormaterial layer and another portion that is epitaxially aligned to saidsemiconductor fin extends to a top surface of said extended sourceregion or to a top surface of said extend drain region.
 7. Thesemiconductor structure of claim 1, wherein said top surface of saidsingle crystalline semiconductor material layer has a (001) surface andsaid semiconductor fin comprises a (001) top surface, (110) sidewallsurfaces, and (1 10) end walls.
 8. The semiconductor structure of claim1, wherein a portion of said extended source region underlies said firstend portion, and a portion of said extended drain region underlies saidsecond end portion.
 9. The semiconductor structure of claim 8, wherein agrain boundary in said extended source region underlies said first endportion, and a grain boundary in said extended drain region underliessaid second end portion.
 10. The semiconductor structure of claim 1,wherein sidewalls and end walls of said insulator layer are verticallycoincident with end walls and sidewalls of said first end portion andsaid second end portion.
 11. A method of forming a semiconductorstructure comprising: forming a semiconductor fin on a stack, frombottom to top, of a single crystalline semiconductor material layer andan insulator layer; forming a gate stack over said semiconductor fin;forming a gate spacer around said gate stack; physically exposing afirst portion and a second portion of a top surface of said singlecrystalline semiconductor material layer; and forming an extended sourceregion on said first portion and an extended drain region on said secondportion by selective deposition of an epitaxial semiconductor materialon said first portion, said second portion, and physically exposedsurfaces of said semiconductor fin.
 12. The method of claim 11, whereinsaid physical exposure of said first and second portions of said topsurface of said single crystalline semiconductor material layer isperformed by anisotropically etchings physically exposed portions ofsaid insulator layer employing said semiconductor fin, said gate stack,and said gate spacer as an etch mask.
 13. The method of claim 11,further comprising forming a source region and a drain region in saidsemiconductor fin by implanting dopants into said semiconductor finemploying said gate stack as an implantation mask, wherein anunimplanted portion of said semiconductor fin constitutes a body region.14. The method of claim 13, further comprising doping said extendedsource region and said extended drain region with dopants of a sameconductivity type as dopants implanted into said source region and saiddrain region.
 15. The method of claim 11, wherein said extended sourceregion is formed on a sidewall of said insulator layer that isvertically coincident with a sidewall of said semiconductor fin, andsaid extended drain region is formed on another sidewall of saidinsulator layer that is vertically coincident with said sidewall of saidsemiconductor fin.
 16. The method of claim 11, wherein said physicalexposure of said first and second portions of said top surface of saidsingle crystalline semiconductor material layer is performed by:anisotropically etchings physically exposed portions of said insulatorlayer employing said semiconductor fin, said gate stack, and said gatespacer as an etch mask; and laterally recessing said insulator layer.17. The method of claim 11, wherein one of said extended source regionand said extended drain region includes a portion that is epitaxiallyaligned to said single crystalline semiconductor material layer andanother portion that is epitaxially aligned to said semiconductor fin.18. The method of claim 17, wherein a grain boundary between saidportion that is epitaxially aligned to said single crystallinesemiconductor material layer and said another portion that isepitaxially aligned to said semiconductor fin extends from a surface ofsaid insulator layer to a top surface of said extended source region orto a top surface of said extended drain region.
 19. The method of claim17, wherein a grain boundary between said portion that is epitaxiallyaligned to said single crystalline semiconductor material layer and saidanother portion that is epitaxially aligned to said semiconductor finunderlies a portion of said semiconductor fin.
 20. The method of claim11, wherein said extended source region and said extended drain regionare formed by: selectively depositing a semiconductor material on saidfirst and second portions of said top surface of said semiconductormaterial layer and on physically exposed surfaces of said semiconductorfin; and patterning said deposited semiconductor material, wherein afirst remaining portion of said deposited semiconductor material is saidextended source region, a second remaining portion of said depositedsemiconductor material is said extended drain region.